The concluding volume in the magisterial historical tetralogy Richard Rhodes calls "The Making of the Nuclear Age" bears a weighty subtitle that hints at its somewhat discursive nature.

"The Twilight of the Bombs: Recent Challenges, New Dangers, and the Prospects for a World Without Nuclear Weapons" also is perhaps the most journalistic (though Rhodes always has been as dogged a reporter as he is a researcher) and prescriptive of the volumes in this remarkable series.

That series began with the Pulitzer Prize-winning "The Making of the Atomic Bomb," one of the rare accounts of atomic origins praised by physicists, historians and politicians of both parties alike. It was followed by "Dark Sun: The Making of the Hydrogen Bomb" and, three years ago, by "Arsenals of Folly: The Making of the Nuclear Arms Race." The latter cast vital new light on the roles Mikhail Gorbachev, who was traumatized by the realization that all the horrific damage done by the Chernobyl reactor meltdown could have been duplicated by a single 12-kiloton nuclear bomb, and Ronald Reagan, the Cold Warrior brave enough to dream of a nuclear-weapon-free world, played in bringing the Soviet-American arms race to an end.

Rhodes writes in his new book that he originally intended the book's material to be part of "Arsenals of Folly," and he has made a sound decision in letting it stand on its own. The difference in tone between this volume and the other three seems, in this context, appropriate — indeed, required — because giving this history such searching scrutiny without reaching for intellectual and moral conclusions would be somehow unnatural. "I've always felt that these four books that I've written are kind of a tragic epic of the 20th century," Rhodes recently told an interviewer. "In the epigraph of my book it says, 'Mankind invents the means of its own destruction.' And where does the human race go from that? We're still mixed in with all of that…."

Nuclear weapons, he continues, are "vast destructive forces encompassed in this small, portable mechanism. They have no earthly use that I can see except to destroy whole cities full of human beings … There's a reason why no one has exploded one in anger since 1945. The risk is too great."

One of the subtle insights Rhodes magnifies here is the idea that the long cold peace between the United States and Soviet Union was a more precarious arrangement than conventional opinion usually credits, and that the two countries' sometimes joint, sometimes separate efforts — usually secret — to prevent nuclear proliferation were, in the long run, more efficacious than the strategic doctrine of mutually assured destruction. "The Twilight of the Bombs" brims with intriguing anecdotes, often offered only in passing. For example:

"In 1983, shaken by the Reagan Administration's belligerent military buildup, and misjudging the intent of a major NATO field exercise in West Germany called Able Archer, which included a practice run-up to nuclear war, the Soviet leadership under Yuri Andropov had very nearly launched a preemptive nuclear strike against the United States. Though it all but escaped public notice, the Able Archer incident was the Cuban Missile Crisis of its day."

Reflecting on its lessons a few years later, Gorbachev would tell former President Richard Nixon that if one superpower kept building weapons, but the other didn't, "the one that arms will not gain anything from it. The weaker party could just explode its nuclear stockpile, even on its own territory, which would mean suicide for it and a slow death for the opponent."

That was the wisdom that led the first President George Bush to unilaterally scrap the huge American arsenal of both land- and sea-based nuclear weapons and to begin the process of helping the new Russia consolidate the old Soviet Union's dispersed nuclear weapons under its sole control. It was that unheralded act of statesmanship — continued under subsequent administrations — that guaranteed that we don't now confront the insecurity of nuclear stocks in four or five other countries of uncertain stability.

Several of the most instructive sections of "The Twilight of the Bombs" shed new, instructive light on these nonproliferation successes. The United States, for example, acted unilaterally to prevent both South Korea and Taiwan from developing nuclear weapons; Brazil and Argentina were persuaded to abandon nuclear ambitions by post-Cold War frankness about the intricacy and expense of such programs. There's a particularly good chapter on how former President Jimmy Carter's personal diplomacy in 1994 helped prevent another Korean War, though curiously nothing about how the so-called Agreed Framework worked out then has fallen to pieces under the weight of North Korea's mendacity and hysterical internal politics. (Some exploration of that problem would have given this book something potentially important to say about the vexed problem of Iran, concerning which the author is silent.)

Rhodes' exploration of the South African nuclear program is particularly enlightening, as cooperation between American and Soviet intelligence along with deftly applied pressure diplomacy delayed Pretoria's weapons program and ultimately led the white supremacist government to destroy its small nuclear arsenal.

There's a lengthy discussion of the run-up to the second Iraq war that doesn't add particularly to our knowledge of those dubious events, though Rhodes does disclose that — before abandoning its nuclear program — Saddam Hussein's regime had built and tested a so-called "dirty bomb" for use against the Iranians. (The test failed because Baghdad's nuclear scientists and engineers were incompetent.) Some of this book's most chilling passages, however, reflect the author's acceptance of analysts' opinions that nuclear terrorism may be much more technically feasible than generally admitted.

In the end, Rhodes' conclusion is that the only safety in a nuclear age is an age without nuclear weapons. How that entirely unreasonable aim can be achieved in an unreasonable world is a difficult proposition. Rhodes speaks to it with great eloquence in his conclusion, which is essentially that of W.H. Auden: "We must love one another or die."